Dietary Cholesterol and Eggs: What You Need to Know

I finally got around to reading that egg study that everyone’s been talking about from the Journal of the American Medical Association (JAMA).  If you didn’t hear about it, it has been covered quite a bit in the media since it’s release just over a week ago.  The study has prompted a re-hash of the egg debate: are they good or bad for you? 

Based on the study results, researchers concluded “higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality in a dose-response manner.”

Oh my, that sounds scary at first glance.  But what do they mean by ‘higher consumption’?

The results compared cholesterol intake of study participants to the US daily average of 285 mg of cholesterol or 3-4 eggs per week.  The key numbers to note: for every additional intake of 300 mg of cholesterol or 1 additional egg per day the study found a 3.24% higher risk of heart disease and 4.43% higher risk of death (absolute risk difference).  For reference, one large egg contains 185mg of cholesterol.

Not as much of a risk between egg consumption and heart disease as implied initially – even the researchers admit “the strength of these relationships is modest”.  We’re also talking about excess egg and cholesterol intake above average.  There are a few significant limitations that most of the media has missed resulting in unnecessary confusion and fear about eating eggs, so let’s take a closer look.

Limitations of the Recent JAMA Egg Consumption Study

The Study Does Not Establish a Cause-Effect Relationship

The researchers analyzed pooled data from over 29,000 adults from multiple cohort studies (six in total) to determine how many eggs on average they ate in a week, and if egg consumption was associated with increased heart disease or death at the end of each cohort follow-up period.  The key word being associated.  This was an observational study, meaning researchers could only observe participants and look at outcomes – there was no treatment given to see if the outcomes were a direct cause of the treatment in one group versus another, like with a randomized control trial.  Cause and effect cannot be determined in an observational study.  Even with an association between egg consumption and heart disease or death, this study cannot say the eggs caused these outcomes.

It Relied on People’s Memory to Determine Intake

Do You Remember How Many Eggs You Ate Last Month?

That’s essentially the question participants were asked.  Food frequency questionnaires (FFQ) were used in each of the cohort studies to determine egg consumption.  These tools use self-reported data to estimate the amount of a certain food people eat.  Additionally, each cohort used a different FFQ so there was variation in the way the question about egg consumption was asked.  This further muddies the results.  The researchers claim to have addressed this with “rigorous methodology to harmonize diet data.”  That’s great and all, but if we’re relying on self-reported data, which already introduces a lot of error, ‘harmonizing’ isn’t going to fix this.

Egg Intake Was Only Measured Once

The researchers measured egg intake just once at the beginning of each individual cohort study.  The follow-up period for the six studies spans 31 years, with an average follow up of 17.5 years.  I’m guessing that out of almost 30,000 people, some of them may have changed their eating habits over the course of a few decades.  Just a hunch.

I think these limitations are important to consider when interpreting the data.  Additionally, the researchers did not assess LDL-cholesterol (a known risk factor for heart disease) of study participants, nor did they account for other risk factors, like stress or income levels.

Dietary Cholesterol Alone Isn’t Likely to Cause High Blood Cholesterol

Dietary cholesterol comes from animal foods we eat like eggs (yolks), meat, poultry, seafood, and dairy products.  We used to think that dietary cholesterol causes an increase to the cholesterol in our blood, but we now know it has little impact for most people.  Specifically, dietary cholesterol doesn’t raise LDL-cholesterol in the blood.  High LDL cholesterol is a major risk factor for heart disease.  Some people are genetically predisposed to have high cholesterol and excessive dietary intake of cholesterol might contribute to higher blood cholesterol for these individuals.  The general population, however, doesn’t need to worry as much about dietary cholesterol.  

Blood cholesterol is impacted by many things, including genetics, trans and saturated fat intake, smoking, physical activity, diabetes, and stress to name a few.  Dietary cholesterol, not so much.

You Can Improve Your Blood Cholesterol and Heart Health and Still Enjoy Eggs

Eggs provide a lot of nutrition in their small packaging. They are a good source of protein, antioxidants, and important vitamins and minerals such as B12, choline, iron, and zinc.  They are also an economical choice compared to some other protein foods.

Here are a few ways you can improve your blood cholesterol and overall heart health, while still enjoying your eggs.

• Ditch the trans fat: In Canada, trans fats have been banned from the food supply as of 2018 (there is a multi-year phase out to this process), so this is less of a concern for Canadians moving forward.  Foods containing partially-hydrogenated oils, such as commercially made pastries and baked goods would be high in trans fat.  Retailers have been given two years to clear their shelves of inventory of these goods, so it’s still wise to read labels of these products.

Trans fats raise unhealthy LDL cholesterol and decrease healthy HDL cholesterol, increasing your risk of heart attack or stroke.

• Enjoy foods containing unsaturated fats – a few ideas:
  • cook and bake with olive, canola, or avocado oil more often than with butter
  • top a salad with almonds, peanuts, cashews, or walnuts, or enjoy them as a snack
  • try some omega-3 containing cold-water fish, like salmon, rainbow trout, sardines, mackerel, or herring (or maybe an omega-3 egg *shrug emoji*)

Unsaturated fats help to lower unhealthy LDL cholesterol and increase healthy HDL cholesterol, helping to reduce your risk of heart attack or stroke.

• Increase your fibre intake: vegetables, fruits, and whole grains are all good sources of fibre.  Adequate intake of fibre helps reduce the amount of cholesterol found in the blood.  (Bonus: it helps with your poops).
• Have fun staying active: find activities you enjoy and have fun doing them.  You don’t have to join Crossfit, or become an Olympic weight lifter – swimming, walking, gardening, playing tag with the kids are all ways you can add physical activity to your day.  Regular physical activity helps reduce your risk of heart disease.
• Make time to chill out: stress is a risk factor for heart disease and stroke. Learning to manage stress is an important part of reducing your risk.

Bottom Line

Given that high blood cholesterol and heart disease are both caused by a variety of factors and taking into consideration the limitations of this study and previous research on this topic, I’d say there’s probably no reason to ditch your breakfast omelet.  For people with a family history of high cholesterol or heart disease, or those living with diabetes, you might benefit from keeping your intake to a moderate amount (2 whole eggs per week), but I’d start with some of the tips mentioned above first.

What do you think about this study?  Are you interested in more reviews of nutrition studies in the news like this one?